Cannabis dependence (CD) is a worldwide public health problem. Treatments are of limited efficacy; one reason may be a failure to address the symptoms of withdrawal, such as craving and disturbances in affect and sleep, that may motivate resumed marijuana (MJ) use. In addition, heavy MJ use and withdrawal can impair executive functioning and thereby interfere with participation in cognitive therapies. The primary aim of this Phase II, single-site, 8-week, double-blind, placebo-controlled randomized clinical trial is to evaluate the efficacy of a novel neurokinin1 (NK1) receptor antagonist, vofopitant (5mg/day), for treating CD in 100 outpatients with current CD. The theoretical rationale for the anti-stress NK1 system as a novel target in CD is based on the neurobiology of abstinence in addiction which involves dysregulation in brain stress and reward systems, i.e., activation of brain stress systems in the amygdala, which vofopitant is hypothesized to normalize. In our Preliminary Studies we show vofopitant significantly decreased precipitated withdrawal symptoms in THC-dependent rats and provide positive results from a proof-of-principle controlled trial of gabapentin (also hypothesized to normalize brain stress circuitry) that found significantly reduced MJ use and withdrawal symptoms, including craving, mood and sleep, and improved executive functioning relative to placebo in 50 CD subjects. The primary hypotheses under test are that vofopitant will significantly improve symptoms of cannabis withdrawal, specifically craving, anxiety, mood and sleep, and reduce MJ use and MJ-related dysregulation of executive functioning and fMRI BOLD response to MJ cues and emotional cues significantly more than placebo in CD outpatients. We will apply the best innovative technology for evaluating the effect of vofopitant treatment on MJ use through a collaboration with Dr. Marilyn Huestis (NIDA/IRP), who will provide analysis of CN-THCOOH concentrations in subjects' weekly observed urine specimens, applying new detection models to identify new MJ use. A further novel aspect of the proposal is the evaluation of executive functioning in the context of a treatment protocol. Potential relationships between MJ use, MJ withdrawal and cognitive functioning will be examined statistically. A further aim of this project is to identify CD individuals most likely to benefit from vofopitant and to measure effects of vofopitant on these factors relative to placebo, thereby clarifying the mechanisms through which NK1 antagonists have efficacy in CD. Potential baseline predictors are: a.) Substance P, ACTH, cortisol and NE, b.) subjective measures of anxiety, mood, insomnia, craving and stress; c.) executive functioning; and d.) fMRI BOLD response to MJ cues, emotional cues and capacity for inhibition in the context of an Affective Go-No-Go task, and functional connectivity during resting state. Given the prevalence of CD and the lack of effective pharmacotherapies, the development of vofopitant as a novel medication for CD may have major public health benefits.